Electrically insulated rail joint means



Feb. 20, 1968 R. w.'Y ouN;;wARb ET 2 ELECTRICALLY INSULATED RAIL JOINTMEANS Filed April 27, 1967 z sheew-sheex 2 F ITHI IIINVENTORS wmm/m/vwwUnited States Patent ()fiice 3,369,752 Patented Feb. 20, 1968 3,369,752ELECTRICALLY INSULATED RAIL JOINT MEANS Robert W. Youngward, ColumbiaHeights, and Alex Kovalchuk, Burnsville, Minn., assignors to MinnesotaMining and Manufacturing Company, St. Paul, Minn., a corporation ofDelaware Continuation-impart of application Ser. No. 503,085, I Get. 23,1965. This application Apr. 27, 1967, Ser.

5 Claims. (Cl. 238-243) ABSTRACT OF THE DISCLOSURE Structural rail jointhaving electrically insulating filament-reinforced resinous joint bars.The joint bars are shaped to nest against the underlying curved surfacesof the rail heads and against the tapered rail bases, but not againstthe rail webs, while clamped with two pairs of bearing plates or pairedsets of bearing plates to join adjacent railroad rails.

The present application is a continuation-in-part of our copendingapplication Ser. No. 503,085 filed Oct.

23, 1965, now abandoned.

Background of the invention Insulated rail joints have long posed adiflicult design problem because such high forces are developed betweenthe rails and the joint bars. Laboratory and field investigations andtheoretical analyses concerning the mechanics of the action of the railjoint have led the industry to conclude that no electrical insulationknown is strong enough to resist these forces without protective steelarmor. Another generally accepted conclusion has been that forsatisfactory serivce, the rail joint should have close to the samestiffness as the full rail. A report to this effect was printed anddistributed by the Association of American Railroads in March 1961,Report No. ER9 entitled Insulated Rail Joint Development and Research.

Description of the prior art In keeping with such belief, until recentlyall insulated rail joints have for many years been constructed in amanner generally similar to the joints illustrated in Corey Patent No.1,174,478 (1916) and Payne Patents Nos. 2,016,214 (1935) and 2,628,784(1953). Such rail joints consist of a pair of steel joint bars bolted tothe rails across the rail juncture with insulating layers of hard fiberbetween the joint bars and rails and surrounding the bolts. Althoughsuch insulation is initially very hard and reasonably waterproof, thepunishment it takes under rolling loads plus its tendency to swell andsoften from moisture, which conditions are compounded by temperaturechanges, destroy its insulating value within relatively short periods oftime. In the past few years, some improvement has been indicated byvulcanizing a layer of very hard rubber on the steel joint bar alongwith a steel protective shim, but the rubber insulation still failswithin undesirably short periods of time. Early tests on this arediscussed in the above-cited Report No. ER-9 of the Association ofAmerican Railroads.

The same report also contains tests on rail joints in which the jointbars themselves were insulating materials such as laminatedresin-impregnated wood or highstrength. plastics. Such structures wereknown as long ago as 1905 as indicated by Lewis Patent No. 783,751 butapparently never earned acceptance by American railroads prior to thepresent invention.

Features of the invention This invention provides for the first time aninsulated rail joint which will withstand for long periods the rigors ofmodern rail transportation even through the joint bars themselves are ofelectrical insulating material, specifically laminated reinforcedplastic. Although such material is of much lower stiffness than issteel, typically oneninth the stiffness of steel, the novel rail jointhas performed exceedingly well in test installations and may welloutlast the best insulated steel rail joints.

The laminae of the joint bars of the novel rail joint comprise a highproportion of fine, high-tensile filaments such as glass embedded inhard, tough, void-free resinous material such as thermoset epoxy resin.By a high proportion is meant that the filaments should comprise atleast one-third of the volume of the laminae. When the filaments arerelatively dense as is glass, they should comprise at least one-half theweight of the laminae. Because of the high forces transmittedlongitudinally through the rails, more than half of the filaments shouldextend in the lengthwise direction, or if a substantial number of thefilaments extend obliquely to the longitudinal, the lengthwise componentof all of the filaments should exceed the transverse component. However,the total transverse (generally vertical) component of all of thefilaments should be at least one-tenth the total longitudinal component,and the joint bars should include laminae providing significanttransverse reinforcement every mils (2.5 mm.) or less through the jointbars, preferably every 50 mils or less. Otherwise the joint bars wouldprematurely develop longitudinal cracks. For ease and economy ofmanufacture, the joint bars preferably are generally flat and of uniformthickness, and hence of a uniform numher of laminae throughout theirlength, one lamina forming a broad outer-facing surface and anotherforming a broad inner-facing surface. When so constructed, the filamentreinforcement of the two surface laminae should extend in the lengthwisedirection of the joint bars.

Other important or preferred features in the construction of theinsulated rail joint of this invention will be considered in connectionwith the drawing.

Description of the drawing FIGURE 1 is a front elevation, in part cutaway, of a preferred embodiment of the rail joint of this invention;

FIGURE 2 is an enlarged elevation, partly in section, taken generallyalong line 2-2 of FIGURE 1; and

FIGURE 3 is a front elevation of another embodiment of the rail joint ofthis invention.

Description of one employment The elongated joint bars 10 illustrated inFIGURES 1 and 2 of the drawing are laminated reinforced plastic, eachlamina being a relatively thin layer of aligned bundles of glassfilaments embedded in thermoset resin. As indicated in the cut-awayportions of FIGURE 1, the filament bundles of the outer laminae extendlongitudinally and provide a broad fiat outer-facing surface 11 whilethe filament bundles of less than half of the inner laminae 12 extendtransversely through the width of the joint bar 10. Each joint bar 10fits against the rails 13, 14 with-its outer-facing surface 11 inclinedfrom the vertical toward the rail head 13a as shown in FIGURE 2. Theupper surface 15 of each joint bar 10 at the edges of the laminae isrounded toward the broad inner-facing surface 16 in order to nestagainst the underlying curved surfaces of the rail head 13a. The lowersurface 17 of each joint bar 10 at opposite edges of the laminae istapered toward the inner-facing surface 16 to nest against the taperedrail bases 13b. The geometry of the inner-facing surface 16 is notcritical as long as it is spaced from the rail web as it is in FIGURE 2.Each joint bar'10 is also provided with six holes or bores 18, each ofwhich is aligned with one of the three attaching holes 19 in each of therails 13, 14. The axes of the bores 18 are inclined from perpendicularto the outer-facing surface 11 at the same angle as the outer-facingsurface 11 is inclined with respect to the vertical. That angle ispreferably about ten degrees as in the illustrated embodiment but may beas little as about five or as much as about twenty degrees from thevertical.

A pair of cast iron bearing plates 20, 21 is mounted against each jointbar with each plate substantially coincident with one half of the fiatsurface 11 extending from one end of the joint bar 10 to the railjuncture but spaced from the other of the plates 20, 21. Each of theplates 20, 21 has a bore 22 aligned with each bore 18 of the contiguousjoint bar '10, and a boss 23 having a substantially vertical fiatouter-facing surface 24 is formed at each bore 22. Tapered washers couldbe used instead of bosses but would be less convenient to use. A

slight depression 25 is machined centrally in the upper v edge surfaceof each joint bar 10 in order to provide clearance from the sharp edgesat the ends of rails 13, 14 which might otherwise cut into the jointbars 13 under the weight of passing railroad equipment.

Sandwiched between the rails 13, 14 is an insulating end post 26 whichmay be formed of any durable, waterresistant insulating material in theshape of the rail crosssection. Molded reinforced resin comprising ahigh proportion of randomly-oriented short glass filaments in thermosetresin has been found to be particularly suitable for use in the novelinsulated rail joint. When the bores 18 and 22 of the joint bars 10 andbearing plates 20, 21 are lined up with the attaching holes 19 in therails 13, -14, the assembly is fastened with bolts 27 and lock washers28,-and this secures the end post 26 in place.

Description of another embodiment Because of the great variety inrailroad rails and the positioning of attaching holes in the rails, ithas been necessary to stock an assortment of the bearing plates 20, 21.In order to avoid doing so, the insulated rail joint of this inventionmay include an individual bearing plate at each attaching hole as shownin FIGURE 3. The two bearing plates conform to substantially the fullheight of the outer side surface of the joint bar 10' and should cover asubstantial lengthwise portion, preferably at least about half, of thejoint bar 10 from oneend to the rail juncture. The plates 20' may toucheach other or be spaced as shown in FIGURE 3 but are spaced from thebearing plate means provided by the plates 21'.

Each of plates 20, 21 is bonded to the joint bar 10', preferably with athermosetting adhesive such as a heatcuring epoxy resin composition.This insures that the outer-facing surfaces 24' of the bosses 23' remainsubstantially vertical during attachment of the joint bar 10' to therails 13 and 14'. Furthermore, it is a convenience in shipping, handlingand assembly to have the bearing plate means already in place.

The design illustrated in FIGURE 3 should enable use of a universalbearing plate, thus greatly simplifying manufacture and inventory.

. The following example describes the construction of an insulated railjoint of this invention which has demonstrated good performance inactual use in a number of test installations.

Example Laminated plastic joint bars were constructed from sheets cutfrom a roll which had been made by drawing through a heated bath ofepoxy resin and hardener a web of lineally-aligned bundles of continuousglass filaments, viz, 200 ends or bundles per inch of ECG 140's, 20 endroving, vinyl silane size. Each end included 204 glass monofilaments ofabout 0.00038-inch diameter. The epoxy resin was made fromepichlorhydrin and bisphenol A and had a Durrans softening point ofapproximately 3040 C., and the hardener was basically isophthalyldihydrazide. After immersion in the bath of resin which was maintainedat about C., the web of glass was passed through squeeze rolls todensify and flatten it to a glasszresin ratio of 64:36 by weight and wasthen contacted with a disposable low-adhesion liner and wound therewithinto roll form.

125 sheets cut from the web were stacked together with the filamentreinforcement predominantly extending in one direction but with thefilaments of every fourth layer extending transversely to thatdirection. The Whole was placed in a heated platen press which had beenpreheated to C. Pressure was gradually applied over a period of eightminutes to 50 p.s.i. to give a thickness of 1% inches. After two hoursin the press at 120 C., the cured panel was removed to anair-circulating oven where it was post-cured for 16 hours at about 138C. After being cooled to room temperature, the panel was sawed andmachined to provide a pair of joint bars as illustrated in the drawing,each 36 inches long in the direction of predominant filamentreinforcement and 4% inches wide. Six holes were drilled at a 10inclination as in FIGURE 2 of the drawing, each 1%; inches in diameter.

Pairs of joint bars of this example have been used in a large number oftest installations on various American railroads with cast iron bearingplates, bolts and glassreinforced-resin end posts as illustrated inFIGURES 1 and 2 of the drawing. Other installations have employed jointbars having only four bores as in FIGURE 3 of the drawing. In only onecase has there been a failure of a joint bar. In isolated cases, bearingplates and bolts have been broken for extraneous reasons. Twoinstallations have been in service for two years as of the filing dateof the present application, one of which is in a special problemlocation where prior art insulated joints have invariably failedprematurely. Other test installations have been in service for shorterperiods but give indication of long life.

Although the rail joint of this invention does not provide the stiffnessafforded by insulated steel rail joints and so permits more flexing atthe joint than was heretofore considered permissible, its constructionis such that it withstands the punishing forces applied to rail jointsfor long periods of time, especially when the fibrous reinforcement ofthe joint bars consists of lineally-aligned bundles of continuous glassfilaments. The novel rail joint is also favored by virtually perfectresistance to water and to other adverse environmental conditions,especially where the reinforcement in the joint bars is glass and theresin is epoxy resin. In contrast, the stiffer armored steel insulatedrail joints of the prior art are quite susceptible to damage where theroad bed is soft or the rail joints are otherwise subjected to severecompressive and abrasive forces resulting in mechanical deterioration ofthe electrical insulating layers. This problem in the prior art has beenparticularly vexing in wet areas. Accordingly, it is believed that theprejudice in the railroad industry against rail joints which do notafford a stiffness approaching that of the rail will be overcome by thisnovel insulated rail joint because of the great resistance to failureafforded by its unique construction. In fact, such prejudice has alreadybeen allayed to a considerable extent as of the fiiing of the presentapplication.

We claim:

1. Means for providing an electrically insulated structural jointbetween adjacent railroad rails which are formed with heads havingunderlying curved surfaces, with tapered bases, and with a plurality ofattaching holes through the web of each rail, said joint means whenassembled comprising:

(A) a pair of elongated, electrically insulating, la-

minated joint bars extending along opposite sides of the rails acrossthe rail juncture, the laminae of the joint bars'comprising a highproportion of fine,

' high-tensile filaments embedded in hard, tough, void-free resinousmaterial, which filaments predominantly extend lengthwise with respectto the bar but have a transverse component of at least each of said bars(1) having broad inner-facing and outer-facing side surfaces andrelatively narrow upper and lower surfaces at the edges of the laminae,

(a) said outer side surface being generally fiat and formedsubstantially by one of the laminae,

(b) said upper edge surface being rounded toward the inner side surface,

(c) said lower edge surface tapering inwardly toward the inner sidesurface,

(2) positioned with respect to said rails with said rounded upper edgenesting against the underlying curved surfaces of the rail heads, withsaid tapering lower edge nesting against the tapered rail bases, withsaid outer side surface inclined toward the rail heads at least aboutfive degrees from the vertical, and with said inner side surface spacedfrom the rail webs,

(3) having a bore aligned with each attaching hole of the rail webs whenthe rail ends are insulatingly spaced,

(B) four bearing plate means positioned in pairs on opposite sides ofthe rails,

(1) each plate means conforming to substantially the full height of andat least about half of the length of one half of the outer side surfaceof one of the joint bars but spaced from the paired plate means,

(2) each pair of plate means having a bore aligned with each bore ofsaid joint bar,

(3) each plate means having a substantially vertical flat outer-facingsurface at each bore, and

(C) adjustable mechanical fastening means extending completely througheach set of bores and holes of the plate means, joint bars and railwebs.

2. The electrically insulated rail joint means defined in claim 1wherein each of said bearing plate means is a single plate formed with aplurality of bores and a boss at each bore to provide said substantiallyvertical flat outer-facing surface.

3. The electrically insulated rail joint means defined in claim 1wherein each of said bearing plate means consists of a plurality ofplates, each of which plates has a single bore and a boss at the bore toprovide said substantially vertical flat outer-facing surface.

4. The electrically insulated rail joint means defined in claim 3wherein each of said plurality of plates is bonded to one of the jointbars.

5. Means for providing an electrically insulated structural jointbetween adjacent railroad rails which are formed with heads havingunderlying curved surfaces, with tapered bases, and with a plurality ofattaching holes through the web of each rail, said joint means whenassembled comprising:

(A) a pair of elongated, electrically insulating, laminated plasticjoint bars extending along opposite sides of the rail juncture, eachlamina of the joint bars comprising a high proportion of lineallyalignedbundles of continuous glass filaments embedded in hard, tough, void-freethermoset resinous material, which filaments predominantly extendlengthwise with respect to the bar but have a transverse component of atleast 10%, each of said bars (1) having broad rectangular inner-facingand outer-facing side surfaces and relatively narrow upper and lowersurfaces at the edges of the laminae,

(a) said side surfaces being flat and parallel to each other and eachformed substantially by one of the laminae,

(b) said upper edge surface being rounded toward the inner side surface,

(c) said lower edge surface tapering inwardly toward the inner sidesurface,

(2) positioned with respect to said rails with said rounded upper edgenesting against the underlying curved surfaces of the rail heads, withsaid tapering lower edge nesting against the tapered rail bases, withsaid outer side surface inclined toward the rail heads at least aboutfive degree from the vertical, and with the inner side surface spacedfrom the rail webs,

(3) having a bore aligned with each attaching hole of the rail webs,

(B) four metal bearing plates positioned in pairs on opposite sides ofthe rails,

(1) each plate having a flat surface substantially co-incident with halfof the outer side surface of one of the joint bars and spaced from thepaired plate,

(2) each pair of plates having a bore aligned with each bore of saidjoint bar,

(3) each plate having a substantially vertical flat outer-facing surfaceat each bore,

(C) an insulating end post sandwiched between therails, and

(D) adjustable mechanical fastening means extending completely througheach set of bores and holes of the plates, joint bars and rail webs.

References Cited FOREIGN PATENTS 1,373,422 8/1964 France.

ARTHUR L. LA POINT, Primary Examiner.

R. A. BERTSCH, Assistant Examiner.

